ISLAMABADâ€”The Pakistan army acknowledged Wednesday that at least 45 civilians died in a military air strike targeting Taliban leaders last weekend, an admission which could fan domestic criticism of the U.S.-backed war effort against Islamic militants.

General Athar Abbas, the chief military spokesman, said the civilians were killed when Pakistani jets bombed a suspected militant hideout in Sera Vela village which is located in the Khyber tribal region in the northwest of the country near the border with Afghanistan.

The military, which rarely confirms civilian deaths, had earlier denied a report by Pakistani newspaper Dawn that more than 60 civilians were killed in the attack. The dead had gathered around a compound used by Taliban militants that was targeted by a Pakistani air force strike, Gen. Abbas said. He didn't detail how many militants died in the action.

Many of those killed belonged to the Kookikhel tribe, which has opposed the Taliban. Some retired army and paramilitary soldiers living in the area were among the dead and injured. Kashmalo Khan, a 63-year-old retired soldier whose right leg was fractured, said he lost 11 family members in the strike.

Washington has praised Pakistan for success in battling Islamic militants in its tribal areas, a semi-autonomous zone which has been used by Taliban and al-Qaeda leaders for years as a base to plan attacks against U.S. forces in neighboring Afghanistan.

The military, aided by unmanned U.S. drone strikes, has since last year killed a number of top Pakistan Taliban leaders who were operating from the tribal region of South Waziristan. The Pakistani military believes that militants who survived those attacks have taken refuge in Khyber and Orakzai, another tribal area.

Since late last year, stepped up military operations in Orakzai have forced more than 200,000 people to leave their homes in the area, the United Nations said this week. That added to an estimated 1.3 million people who had already been displaced by fighting in the tribal regions.

Mounting numbers of civilian deaths, added to a growing refugee crisis, could further undermine the Pakistani military's war against Islamic militants in the border regions, analysts say. U.S. drone strikes are already unpopular among many Pakistanis.

"The incident will further complicate the Pakistani military's efforts to mobilize public support for its anti-Taliban campaign," said Rifaat Hussain, a professor of security studies at Quaid-e-Azam University in Islamabad. "Family of the victims could become easy recruits for the militants."

Although weakened, the Pakistan Taliban, which is linked to the Afghan Taliban, have been able to evade capture in the mountainous tribal regions and continue to carry out attacks. Earlier this month, the Pakistan Taliban claimed responsibility for a suicide attack on a pro-government meeting in Pakistan's North West Frontier Province, which killed more than 50 people.

It remains unclear who is directing the Pakistan Taliban, known as Tehrik-e-Taliban Pakistan, after its leader Baitullah Mehsud was killed by a U.S. missile strike in August 2009. Hakimullah Mehsud, who took over the leadership, was reported to have been injured in an attack on his hideout in February but it remains unclear whether he was killed.